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Rock Fracture Under Stress Gradients.
Final rept. Dec 72-Dec 73,
UTAH UNIV SALT LAKE CITY DEPT OF MECHANICAL ENGINEERING
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Rates of loading were varied for Westerly granite and Nugget sandstone notched tension and beam bending specimens, giving loading times from 100 microseconds to 150 seconds. The nominal fracture strength increased with increasing loading rate for all specimen configurations studied, and no consistent trends in the rate effect with specimen stress concentration could be observed. Compression tests of Westerly granite and Nugget sandstone plates with circular and elliptical holes showed an insensitivity of fracture stress to stress concentration in compression, as has been shown previously in tension. Fracture occurred in compression in plate specimens where tension failure had been expected. These last mentioned results are not well understood. Author
APPROVED FOR PUBLIC RELEASE